This invention relates to a method for extruding metal tubes to form full length and partial length longitudinal grooves within the interior wall of the tube so that the tube may be used, for example, for valve body sleeves for controlling oil flow in vehicle steering mechanisms and for other articles.
In the past, the manufacture of metal tubes with full length and partial length grooves or channels formed within the interior of the tubes has been difficult and relatively expensive. An example of this type of product is an automotive vehicle valve body or sleeve which forms part of a valve which controls the flow of oil in the vehicle steering mechanism. Such a valve body or sleeve is formed of a metal tube which has, for example, four full length channels extending longitudinally through its interior surface. In addition, it may have, for example, four partial length channels which are located only in the intermediate portion of the sleeve. That is, these partial length channels terminate a considerable distance from the opposite ends of the sleeve.
In the past, these sleeves have been manufactured by broaching the number of channels that are required along the full length of the interior of the tube. Then the opposite ends of the partial channels were blocked off.
One way that has been used in the past to block off the ends of the partial channels involved, first, forming the partial channels of a shallower depth than the full length channels. Then, the opposite ends of the interior wall surface of the tube were cut away to the depth of the shallower partial channels. Next, rings were fitted within the cut-away end portions so that each of the rings blocked off one of the opposite ends of the shallower, partial channels. Meanwhile, the rings overlapped the end portions, which were not cut away, of the full length channels. Because of the rings, the opposite, overlapped end portions of the full length channels were of shallower depth than their middle parts. However, the full length channels extended continuously to the opposite ends of the tube.
By the foregoing method, a number of partial and full length channels were provided within an article, such as a valve body sleeve. These channels were then communicated either with each other or to other places by means of drilling holes in the sleeve. In the case of a valve body sleeve an interior spool was inserted within the tubular sleeve. Thus, by appropriate endwith or rotative motion the flow of oil was controlled through the various full length and partial length channels.
In this type of valve construction, the valve body or sleeve requires considerable machining and also, requires three separate parts which must be assembled.
In the past, cold forming processes for extruding thin wall metal tubes either cold or with some heat, have been available. Examples of these cold forming extrusion processes are illustrated, for example, in my prior U.S. Pat. No. 4,277,969 issued July 14, 1981 for a method of cold forming tubes with interior thicker wall sections, and No. 4,292,831 issued Oct. 6, 1981 for a process for extruding a metal tube with inwardly thickened end portions. Other examples of such cold forming processes are disclosed in my U.S. Pat. Nos. 3,837,205 issued Sept. 24, 1974 for a process for cold forming a metal tube with an inwardly thickened end, U. S. Pat. No. 3,886,649 issued June 3, 1975 for a process for cold forming a metal tube with an inwardly thickened end, U.S. Pat. No. 4,301,672 issued Nov. 24, 1981 for a process for forming semi-float axle tubes and the like, U.S. Pat. No. 4,487,357 issued Dec. 11, 1984 for a method for forming well drill tubing and U.S. Pat. No. 4,435,972 issued Mar. 13, 1984 for a process for forming integral spindle-axle tubes.
The cold extrusion processes disclosed in the above-mentioned patents are relatively inexpensive in mass production manufacture of metal, tubular parts. Thus, the invention of this present application relates to utilizing a cold extrusion process, but adapting such a process for the production of tubes having some full length and some partial length grooves or channels formed in their interiors so as to produce parts such as the valve body sleeves and the like less expensively.